linux-kernel - Re: [PATCH] mm/vmalloc: leave lazy MMU mode on PTE mapping error

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Message-ID: <cb71d9f4-aaae-4240-88f5-50a745717f22@arm.com>
Date: Mon, 23 Jun 2025 14:31:48 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: leave lazy MMU mode on PTE mapping error

On 23/06/2025 14:03, Alexander Gordeev wrote:
> On Mon, Jun 23, 2025 at 01:37:11PM +0100, Ryan Roberts wrote:
>> On 23/06/2025 08:57, Alexander Gordeev wrote:
>>> Function vmap_pages_pte_range() enters the lazy MMU mode,
>>> but fails to leave it in case an error is encountered.
>>>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
>>> Closes: https://lore.kernel.org/r/202506132017.T1l1l6ME-lkp@intel.com/
>>> Fixes: 44562c71e2cf ("mm/vmalloc: Enter lazy mmu mode while manipulating vmalloc ptes")
>>> Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
>>
>> Ouch, sorry about that! The patch looks good to me so:
>>
>> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
>>
>> I wonder an aditional Fixes: should be added for Commit 2ba3e6947aed
>> ("mm/vmalloc: track which page-table levels were modified") though? That's the
>> one that added the "*mask |= PGTBL_PTE_MODIFIED;" which would have also been
>> skipped if an error occured before this patch.
> 
> Good catch! I think it certainly needs to be reported with Fixes
> and I even doubt whether your commit should be mentioned at all?

Well I would certainly argue that my patch is broken as is. So happy to have 2
Fixes: tags. But I'm not really sure what the rules are here...

> 
>> Thanks,
>> Ryan
> 
> Thanks!